Little League and USA Baseball have focused in recent years on total pitch count limits[1] and rest periods between pitching outings as ways to reduce the number of pitching injuries. Some baseball experts believe, however, that per inning pitch counts are more important than total pitch counts and that removing pitchers when they exceed per inning pitch count limits and show signs of fatigue will do more to protect the arms of young pitchers than focusing exclusively on total pitch count limits.

For example, MomsTeam's baseball expert, John Pinkman, recommends as follows:

Goal: 15 pitches per inning

1 inning at 25 to 30 pitches okay; 2 in a row done for the day

1 inning at 35 pitches or more: done for the day

Another set of guidelines comes from pitching coach Ron Wolforth of Pitching Central and the Texas Baseball Ranch1

Pitches per inning

Action

12 to 15 (ideal)

Pitcher stays in game unless shows signs that he is tired (see signs of fatigue below)

18 to 22

Pitcher is more closely monitored for signs that he is tired (e.g. shows signs of fatigue)

23 to 30

Under normal circumstances, pitcher is replaced once he reaches 30 pitches or has a second inning exceeding 23 pitches, but is allowed to finish the inning or go to 35 pitches before replacement.

Remove if show signs of fatigue (see below); replaced at that point, even mid-inning

If pitcher already has logged a 22-25 pitch inning, replaced when reaches 25 pitches, even if mid-inning.

Exceptions:

Veteran pitcher

Later in season (built foundation)

Average velocity numbers and pitch location remain solid

30+

Pitcher is replaced. Veteran pitcher, late in season, might be allowed to finish inning, but "young arm is simply done for the night."

"I am completely convinced per count per inning is vastly more important than total pitch count," writes Wolforth, arguing that a pitcher who throws 62 pitches over two innings (31 per inning) is at "far greater risk" of an arm injury than a pitcher who throws 104 pitches, but spread out over 7 innings (14.8 per inning) [the number permitted under Little League's 2010 rules[1] for a 17-18 year old pitcher].

In fact, Wolforth argues, he doesn't "worry much about total pitch count" for a pitcher, as long as he is well-conditioned[2] and physically prepared, but focuses instead on monitoring pitch per inning and makes the decision about whether to remove the pitcher on those numbers.

Three signs that pitcher is tired

As long as a pitcher stays between 12 and 18 pitches per inning, Wolforth believes the pitcher's "got the game as long as he wants it", provided he doesn't show any of the following three signs of fatigue:

Average radar velocity drops 3-5%. For example, Wolforth says, a pitcher averaging 80 mph in the first inning and 76-77 mph in the fifth has "had enough. Go get him." [Note: this is proper use of radar gun; pitcher not "throwing to the gun"]

Consistently elevated fastball: Even if pitch velocity isn't down, if the pitcher throws 3 to 5 fastballs in a row 4-6 inches above where it was when he was fresh, he needs to be monitored closely. Wolforth rejects the "lost his release point" philosophy. To him, it is "either a fatigue issue, a preparation-mechanical-conditioning issue or a focus-concentration issue. ... As a general rule," says Wolforth, "if a young pitcher unintentionally elevates his fastball for two consecutive hitters, I'll go talk to him. If he doesn't make an adjustment on hitter #3, he's had enough."

Missing locations high or low. Wolforth believes that "the scatter pattern of wild high and in[side] to the arm side and wild low and out[side] to the glove side is almost always a sign of significant fatigue and mechanical inefficiency. If this pattern is not corrected quickly - certainly within two hitters, the pitcher - veteran or rookie - is finished for the day.

Throwing strikes

To those who say that an elevated fastball or wildness describe one of their pitchers in the first inning when he is presumably fresh, Wolforth says the pitcher needs to work a lot more on his mechanics: "If a young man throws like #2 and #3 when he is fresh, he will have real trouble getting 3 outs in 15 pitches." In other words, he says, pitch counts aren't the problem, "'pitching' is." As a pitcher becomes more effective and efficient, in other words, throws more strikes, his pitch count will automatically come down.

Little League and USA Baseball have focused in recent years on total pitch
counts[1] and rest periods between pitching outings as ways to reduce
the number of pitching injuries. Some baseball experts believe,
however, that removing pitchers from games based on the number of pitchers they throw per inning and/or when they exhibit certain signs of
fatigue will do more to protect the arms of young pitchers than total pitch count limits.